Top coating paint for automobiles generally contains, as a film-forming binder, a combination of a hydroxyl group-containing polymer and a melamine curing agent. The cured film obtained from the melamine curing system, however, has poor acid resistance and is damaged by acid rain which has recently become one of serious problems. The damage of the film provides poor appearance.
In order to overcome the above mentioned defects, the present inventors have proposed novel coating compositions without the melamine curing agent in Japanese Kokai Publications 45577/1990 and 287650/1991. The proposed coating composition cures by means of the reaction of acid and epoxy and therefore has good acid resistance. In this curing system, however, if degree of crosslinking is set high enough to impart good weather resistance to the cured film, the resulting film has poor elongation and is stiff and brittle. The stiff and brittle film has poor mar resistance and is easily damaged by scratch. It is therefore difficult for the proposed coating compositions to employ as top-coating paint. It is desired to develop top-coating paint which has not only excellent acid resistance but also high mar resistance, water repellency and good stain resistance.